The main objectives of this investigation are (a) to demonstrate the existence of a spermatozoal cholinergic system consisting of choline acetyltransferase (ChA), acetylcholine (ACh), cholinergic receptor (AChR) and acetylcholinesterase (AChE), and (2) to study the significance of ChA-ACh-AChR-AChE system to sperm motility, viability and fertilizing capacity. The spermatozoa from humans, bulls, rats, and rabbits will be used in these studies. The specific aims include: (1) demonstration of ACh in spermatozoa by gas chromatography-mass spectrometry, (2) characterization of sperm ChA, (3) demonstration of the enzymes necessary for the formation of precusors (acetyl-CoA, choline) for ACh synthesis in spermatozoa, (4) evidence for choline uptake system in spermatozoa, (5) characterization of the cholinergic receptor in spermatozoa, and distribution of 14C-nicotine and 125I-alpha-bungarotoxin binding proteins in sperm fractions (6) effects ChA-inhibitors on sperm motility (in vitro) (7) antifertility effects of nicotine and ChA-inhibitors in rats, and (8) effects of antifertility agents (cyproterone acetate, alpha-chlorhydrin and trimethylophosphate) on the levels of ACh, ChA and acetate thiokinase in epididymal spermatozoa in the rat. The results of this investigation may be useful to (1) explain the role of ACh in the regulation of sperm motility (2) understand certain types of infertility in men who ejaculate immotile sperm (3) explain transient infertility among male smokers, and (4) develop antifertility agents.